Biden will be upbeat and energetic. He will spout a lot of nonsense. He can bluff his way through a debate especially with a moderator who is in the tank for the Democrats. He will attack but try his best to not come across as an ill-tempered bully. He will probably make some gaffs but that won't matter because everyone expects that.
Ryan will be lower key and straight forward. He will have a lot of facts. I don't really know anything about his actual debating skills.
When it is over, all the analysts and talking heads except for most of the ones on Fox will declare Biden won handily and Ryan lied. I doubt either campaign will get much of a boost or be hurt much by the debate results.